1. Field of the Invention
This invention relates to a method and apparatus for controlling a windscreen wiper, for example for a motor vehicle.
2. Description of Related Art
The self-evident objective of a windscreen wiper system is to maximise the driver's visibility of the road ahead. Whilst under conditions of heavy rainfall this objective is likely to demand the highest possible sweep rate, under light rainfall conditions the sweep rate must be reduced to avoid smearing, blade judder and excessive wear in the system. Known methods for adjusting the sweep rate are variation of the sweep time (a multiple speed wiper motor) and variation of the delay between consecutive sweep cycles. Known systems incorporate switched motor speeds, switched delays and variable delays, all of which are controlled manually by the driver. Manual adjustment of sweep rate is a source of distraction to the driver, particularly in heavy traffic.
It is also known to employ optical or electrical sensing means for the detection of moisture on a windscreen for the purpose of activating windscreen wipers. However, such devices have not provided an economical and effective means of controlling windscreen wipers to optimise visibility and manual intervention by the driver has still been required. It is an object of the invention to provide a method and apparatus for controlling a windscreen wiper which is effective automatically to adjust the rate of operation of the wiper in dependence on the mean moisture level on the windscreen.